The gatekeepers of our intestine's immunity
The inside of our intestines are outside of our body, so obviously we need...
Wait, what did he just write?
The inside of our intestine's are outside of our body?
Think about it: If you would swallow a tiny camera and follow it's course around you stomach, small intestine, colon and rectum, you would find no connection to the rest of our body, just a long, dark tunnel covered with a glistening, soft surface and a lot of, er, poo. Yep, our gastrointestinal system is nothing but one elastic, well sealed tube connecting our ass and mouth.
The Peyer's patches (named after swiss anatomist Johann Conrad Peyer (1653-1712) are part of our natural defense against unwanted intruders, representing an important part of our lymphatic system and are multiple small follicles of lymphoid tissue in the lower part of the small intestine called Ileum and are just about the size of small peas.
There are three major lymphatic organs guarding our gastro intestinal tract: our tonsils, the peyer's patches and the appendix, all three characterised by an abundance of immunocompetent cells (mainly B - Lymphocytes and dentritic cells) who survey the contents of our GI tract and react by releasing messenger molecules to alert the rest of our immune system and start proliferation.
If you can get hold of a piece of human ileum, you can actually feel them just below the surface.
But you should ask your local anatomy professor first.